The development of commercially viable engines having very high thermal efficiencies (TE) is a global challenge, as the demand for ground transportation increases while being constrained by limited petroleum supplies and the need to reduce CO2 emissions. Increasing the efficiency of engines that operate on gasoline (or similar alternative fuels) offers high potential for improvement since current gasoline spark-ignition (SI) engines are considerably less fuel efficient than diesel engines. Low-temperature gasoline combustion (LTGC), sometimes called homogeneous charge compression ignition (HCCI) or other names in the literature, is a relatively new combustion process that has been shown to have promise for automotive- and truck-sized engines. These LTGC engines can be highly fuel efficient, and the load-range of these engines has been improved, with operation from idle to high loads similar to those of turbocharged diesel engines having been demonstrated. However, controlling the autoignition process, which directly affects combustion timing, over the load-speed map remains a significant technological challenge.